I am convinced that London Bridge exists in multiple dimensions. No matter how many times I go there, I never figure out the complex, multi-tiered system of wormholes by which one is supposed to leave the station.

So before I could make it to the theatre on Sunday night, to see the Factory company's semi-secret, semi-improvised take on Hamlet, I was forced to perform a brisk survey of the streets, running in the same direction but arriving back where I started, searching for the Southwark Playhouse. When you are clutching a frying pan, as I was, this attracts some bemused looks.

Why was I clutching a frying pan? Well, for the evening's underground theatricals, I had been told that the audience must provide the props. When I finally found the theatre, I ran straight into the back of famous actor Ewan McGregor, enjoying a night off from Othello. You can fault his Iago, but not his commitment to Shakespeare: he had brought an old accordion, a better class of prop than my greasy implement, but I daresay his salary is larger than mine.

Once seated, we were introduced to the wheeze. The actors, who do it for love not money, perform in whichever space is at hand - the Southwark Playhouse today, an abandoned glue factory tomorrow, say. Each knows the script of Hamlet inside out. They play Scissors/Papers/Stone at the beginning to decide who plays whom, and then perform the tragedy making up all movements and stage directions as they go along and grabbing props from the audience - a traffic cone, a butternut squash, a well-behaved human baby, etc.

It would be a mere gimmick if the actors didn't pull it off with such inspired conviction - more conviction, indeed, than there was to be found in the last dreary Hamlet I saw (Trevor Nunn's overpraised effort at the Old Vic).

So Laertes warned his sister Ophelia about men's motives fingering a phallic marrow; the Player King improvised a song as his campadre worked out how to play McGregor's accordion; and Claudius brilliantly employed a candle in place of a letter, reading the flame as if it were text.

Most daring, Hamlet plucked the baby from the arms of its mother to illustrate his "What is this quintessence of dust?" speech (you know, the one Richard E Grant does in Withnail & I). It was heart-in-the-mouth theatre, unbearably poignant, unrepeatable, screw Health and Safety.

Factory's Hamlet exists in the dimension where real life meets the stage, makes you see the dramatic in the everyday, the everyday in the dramatic.

Just a shame they never used the old frying pan.

See www.seehamlet.co.uk

* Yeah, I know that's from Macbeth - but I don't have my folio to hand.